The present invention relates to a meter dial illuminating device, and more particularly to a meter dial illuminating device in which a portion of a dial except that where characters and a scale are indicated is formed of a light transmitting material, and a front surface of the dial is illuminated by a light transmitted through said light transmitting portion, thereby providing a dial illuminating device which may improve visibility with less fatigue of the eyes without increasing costs and enlarging a size of the meter.
Conventionally, in a meter such as a speedometer and a fuel gauge for a vehicle, characters and a scale, etc. indicated on a meter dial are formed of a light transmitting material, and the other portion is formed of a light cutting material. A light incident upon a back surface of the dial in the night is transmitted through the light transmitting characters and scale formed on the dial to thereby enable a driver to visually perceive the characters and the scale.
However, there is generated an excessively sharp contrast in brightness between the characters and the scale which are illuminated and the other portion not illuminated, which causes fatigue of the eyes.
To eliminate such a defect, there has been used a dial illuminating device as shown in FIG. 1, which is designed to also illuminate a front surface of the dial.
A dial 4 is mounted to a meter driver 2 fixed to a bottom of a meter case 1 with a light guiding plate 3a interposed between the dial 4 and the meter driver 2. A light emitted from a bulb 5a provided at the bottom of the meter case 1 is guided from one end of the light guiding plate 3a through the same to a back surface of the dial 4. The guided light is transmitted through the light transmiting characters and scale formed on the dial 4 to a front surface of the dial 4. On the other hand, another bulb 5b is provided at the bottom of the meter case 1, and another light guiding plate 3b is provided on the meter case 1 or a background 6. A light emitted from the bulb 5b is guided through the light guiding plate 3b to a hole 6b formed through a horizontal wall 6a of the background 6, and the light is illuminated through the hole 6b onto the front surface of the dial 4.
The background 6 is provided at a front opening of the meter case 1 to act as a mask for concealing an outer peripheral portion of the dial 4 and the meter driver 2. A front glass plate 7 is provided in front of the background 6 so as to prevent a dust from depositing on the dial 4 and from penetrating into the meter case 1. A rotating shaft 8 is projected from the meter driver 2 through center hole of the dial 4, and a self-illuminating pointer 9 is mounted on the rotating shaft 8. PG,4
Sockets 11a and 11b for receiving the bulbs 5a and 5b are mounted on a back surface of the meter case 1 with a feeder wiring board 10 interposed between the back surface and the sockets 11a and 11b, so that the bulbs 5a and 5b may be switched on at night.
A color filter 12 is provided between the hole 6b and the light guiding plate 3b so as to color the light illuminated through the hole 6b onto the front surface of the dial 4. A light shielding plate 13 is provided to prevent the light illuminated through the hole 6b from being directly leaked through the front glass plate 7, causing reflection of the light on a windshield and the like of the vehicle to hinder a front visible field of the driver when driving.
FIG. 2 is an elevational view of a speedometer using the dial 4 as mentioned above, and FIG. 3 is a cross-sectional view of the dial 4. As shown in FIG. 3, the dial 4 is constructed such that a chromatic translucent layer 4b and a white translucent layer 4c are formed on a transparent base member 4a in this order, and a black opaque layer 4d is formed on the white translucent layer 4c except a portion where the characters and the scale are indicated. With this construction, the characters and the scale are visualized in white when the light is off, while they are visualized in chromatic color of the layer 4b when the light is on.
In the prior art device as mentioned above, the front surface of the dial 4 through which the light from the bulb 5a is transmitted at the location of the characters and the scale is illuminated by guiding the light from the bulb 5b through the light guiding plate 3b, the color filter 12 and the hole 6b formed through the horizontal wall 6a of the background 6 to the front surface of the dial 4, so as to reduce the difference in brightness on the dial 4. Therefore, it is necessary to provide additional parts of the light guiding plate 3b, the color filter 12 and the light shielding plate 3, which causes an increase in parts cost and installation cost and also causes an increase in weight due to an enlarged size of the meter including the additional parts. Furthermore, the transmittance illumination effect of the characters and the scale is reduced by the light illuminating the front surface of the dial, and thereby a commodity value becomes low. In addition, a part of the light transmitting the front surface of the dial is reflected on the windshield to dazzle the driver.
Accordingly, it is an object of the present invention to provide a meter dial illuminating device which may reduce the difference in brightness between the portions of the characters and the scale on the dial and the other portion of the dial to eliminate fatigue of the eyes, without using numerous additional parts to illuminate the front surface of the dial.
According to the present invention, in a meter dial illuminating device for illuminating a dial by a light incident upon a back surface of the dial and transmitted through a front surface of the dial, the improvement is characterized in that a portion of the dial except at least characters and a scale is formed of a light transmitting material, so as to illuminate the front surface of the dial by the light transmitted through the portion.
A relatively large area in comparison with the characters and the scale is formed of the light transmitting material, and the front surface of the dial is designed to be illuminated by the light transmitted through the large area. Therefore, in comparison with the prior art device wherein the light is transmitted through only the characters and the scale, the present invention may provide sufficient illumination effect with a weak light and thereby improve the visibility with no fatigue of the eyes.